More specifically, think of a metal disc like an ordinary circular saw blade, and imagine that the edge of this disc is serrated like an ordinary hacksaw blade. Maybe it should be super-fine, like 25 teeth per centimeter.

So far, in Googling around and looking at tool-friendly sites, I haven't found
this simple thing. I assume that it is because hacksaw blades reciprocate rather slowly, compared to the speed of a circular saw. That doesn't mean one can't be made, though! (That's also why a very large number of fine teeth is probably essential for this Idea to work at all.)

When I read the title, I imagined a kind of bicycle wheel effect with a thin ring of hacksaw blade. It could be attached to an oscillating head like an electric toothbrush - but with more power, obviously. Else you'll just about cut balsa wood.

I can't believe this doesn't exist, but as I have never seen one and none of the links show what [Vernon] is describing I am going to have to bun. Circular saws are very cool but tend to make a bit a a mess of what you're cutting. A blade that would let you use a circular saw to cut with the precision of a bandsaw, whether through metal or wood, would be great.

[UnaBubba], cut-off wheels basically use extreme friction to do their cutting. Lots of heat and sparks is just a natural consequence. Now, I agree that heating is a problem even with hacksaws while cutting. Many is the time I've manually hacksawed through some steel and noticed hot blade and workpiece both. I've never seen sparks, but of course that's probably due to the low speed of cutting.

My notion of lots of very fine teeth (if they be carbide, fine!) is intenced to ensure that any individual "bite" taken out of the workpiece by the blade is as small as possible. Because of being "bitten" out of the steel instead of "frictionally worn" out of the steel, that is why a sawblade should run at least somewhat cooler than a cut-off wheel.

So, to be more specific, since the linked sawblades seem mostly to range from 36-60 teeth, let me compute an ordinary 7-inch (18cm) circular saw blade as having a circumference of about 56cm, and so at 25 teeth per cm, which I suggested in the original text (I see you mentioned 150 teeth/meter or 1.5/cm (--thanks, [UB], wasn't paying close-enough attention), I'm thinking that a circular saw blade having roughly 1400 teeth might run cool enough --especially if you don't try to move the saw through the workpiece too fast!

By the way, I hear that regular circular saw blades do a reasonable job of cutting corrugated iron, provided that you put the blade on backwards so it has a negative(?) rake angle. I'd avoid tungsten tips though, for that application.

Apart from the title being confusing, this is baked a thousand times over. Circular saws with fine teeth, saws with bonded abrasive--tungsten carbide, nitride, diamond...whatever you want. Cooling by air, water based fluid, or oil. It's even possible to saw without teeth at all--using a bronze wheel with an abrasive slurry.

One thing I neglected to mention was the THINness of a hacksaw blade, compared to an ordinary circular saw blade. Those wide blades take big bites, and so no wonder they generate lots of heat and sparks. A narrow circular hacksaw blade should cut more cool-ly partly because of this factor, as well as because of the large number of teeth that has been previously mentioned.

Buy yourself a 130 tooth to a 700 tooth blade for your saw, use a blade backer for stability and report back. Plywood blades carry about 100 teeth and likely are too unstable to use on the wrong material, but I'm not finding anything with more.